Project Summary/Abstract Obesity is a significant public health concern and a well-known risk factor for colorectal cancer (CRC). Western diet, high in calories and fat and deficient in fiber-rich foods, is a key driver of metabolic diseases like obesity and CRC. High-fiber diets including foods like legumes, such as dry beans and lentils, could have favorable effects on underlying biological responses that mediate the obesity-cancer relationship including insulin signaling, chronic inflammation, gastrointestinal motility, gut microbiota changes and the balance between cell proliferation and apoptosis. We propose to build upon our previous research demonstrating that short-term strictly monitored increases in fiber-rich food consumption facilitates weight loss and suppresses biomarkers of cancer risk. The goal of the current research is to conduct a 12-month parallel arm randomized clinical trial featuring pre-portioned entres and strategic nutritional instruction to integrate legumes into a healthy high-fiber diet pattern. Over the course of the intervention participants will receive intense education combined with behavior modification, transitioning to self-directed and finally sustainable maintenance phases. The research will target a diverse population at highest risk for CRC (recruit n=70; 50% males / 50% females), overweight and obese participants with a history of polypectomy, to test whether a high-legume, high-fiber diet will increase weight loss and suppress colonic mucosal biomarkers of cancer risk compared to a control diet. In addition, we will explore potential beneficial effects of the high-legume intervention diet on the microbiome and metabolome, gastrointestinal transit time and on systemic biomarkers of inflammation and insulin resistance. Given the 20-fold differences in CRC between populations consuming high-fiber diets and low-fiber Western diets, the results of this study may demonstrate substantial potential for dietary change to reduce mortality from CRC and other westernized diseases.